src/getty-generator/getty-generator.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <string.h>
  23 #include <errno.h>
  24 #include <unistd.h>
  25 #include <fcntl.h>
  26
  27 #include "log.h"
  28 #include "util.h"
  29 #include "mkdir.h"
  30 #include "unit-name.h"
  31 #include "virt.h"
  32 #include "fileio.h"
  33 #include "path-util.h"
  34 #include "process-util.h"
  35 #include "terminal-util.h"
  36
  37 static const char *arg_dest = "/tmp";
  38
  39 static int add_symlink(const char *fservice, const char *tservice) {
  40         char *from, *to;
  41         int r;
  42
  43         assert(fservice);
  44         assert(tservice);
  45
  46         from = strjoina(SYSTEM_DATA_UNIT_PATH "/", fservice);
  47         to = strjoina(arg_dest, "/getty.target.wants/", tservice);
  48
  49         mkdir_parents_label(to, 0755);
  50
  51         r = symlink(from, to);
  52         if (r < 0) {
  53                 if (errno == EEXIST)
  54                         /* In case console=hvc0 is passed this will very likely result in EEXIST */
  55                         return 0;
  56                 else {
  57                         log_error_errno(errno, "Failed to create symlink %s: %m", to);
  58                         return -errno;
  59                 }
  60         }
  61
  62         return 0;
  63 }
  64
  65 static int add_serial_getty(const char *tty) {
  66         _cleanup_free_ char *n = NULL;
  67
  68         assert(tty);
  69
  70         log_debug("Automatically adding serial getty for /dev/%s.", tty);
  71
  72         n = unit_name_from_path_instance("serial-getty", tty, ".service");
  73         if (!n)
  74                 return log_oom();
  75
  76         return add_symlink("serial-getty@.service", n);
  77 }
  78
  79 static int add_container_getty(const char *tty) {
  80         _cleanup_free_ char *n = NULL;
  81
  82         assert(tty);
  83
  84         log_debug("Automatically adding container getty for /dev/pts/%s.", tty);
  85
  86         n = unit_name_from_path_instance("container-getty", tty, ".service");
  87         if (!n)
  88                 return log_oom();
  89
  90         return add_symlink("container-getty@.service", n);
  91 }
  92
  93 static int verify_tty(const char *name) {
  94         _cleanup_close_ int fd = -1;
  95         const char *p;
  96
  97         /* Some TTYs are weird and have been enumerated but don't work
  98          * when you try to use them, such as classic ttyS0 and
  99          * friends. Let's check that and open the device and run
 100          * isatty() on it. */
 101
 102         p = strjoina("/dev/", name);
 103
 104         /* O_NONBLOCK is essential here, to make sure we don't wait
 105          * for DCD */
 106         fd = open(p, O_RDWR|O_NONBLOCK|O_NOCTTY|O_CLOEXEC|O_NOFOLLOW);
 107         if (fd < 0)
 108                 return -errno;
 109
 110         errno = 0;
 111         if (isatty(fd) <= 0)
 112                 return errno ? -errno : -EIO;
 113
 114         return 0;
 115 }
 116
 117 int main(int argc, char *argv[]) {
 118
 119         static const char virtualization_consoles[] =
 120                 "hvc0\0"
 121                 "xvc0\0"
 122                 "hvsi0\0"
 123                 "sclp_line0\0"
 124                 "ttysclp0\0"
 125                 "3270!tty1\0";
 126
 127         _cleanup_free_ char *active = NULL;
 128         const char *j;
 129         int r;
 130
 131         if (argc > 1 && argc != 4) {
 132                 log_error("This program takes three or no arguments.");
 133                 return EXIT_FAILURE;
 134         }
 135
 136         if (argc > 1)
 137                 arg_dest = argv[1];
 138
 139         log_set_target(LOG_TARGET_SAFE);
 140         log_parse_environment();
 141         log_open();
 142
 143         umask(0022);
 144
 145         if (detect_container(NULL) > 0) {
 146                 _cleanup_free_ char *container_ttys = NULL;
 147
 148                 log_debug("Automatically adding console shell.");
 149
 150                 if (add_symlink("console-getty.service", "console-getty.service") < 0)
 151                         return EXIT_FAILURE;
 152
 153                 /* When $container_ttys is set for PID 1, spawn
 154                  * gettys on all ptys named therein. Note that despite
 155                  * the variable name we only support ptys here. */
 156
 157                 r = getenv_for_pid(1, "container_ttys", &container_ttys);
 158                 if (r > 0) {
 159                         const char *word, *state;
 160                         size_t l;
 161
 162                         FOREACH_WORD(word, l, container_ttys, state) {
 163                                 const char *t;
 164                                 char tty[l + 1];
 165
 166                                 memcpy(tty, word, l);
 167                                 tty[l] = 0;
 168
 169                                 /* First strip off /dev/ if it is specified */
 170                                 t = path_startswith(tty, "/dev/");
 171                                 if (!t)
 172                                         t = tty;
 173
 174                                 /* Then, make sure it's actually a pty */
 175                                 t = path_startswith(t, "pts/");
 176                                 if (!t)
 177                                         continue;
 178
 179                                 if (add_container_getty(t) < 0)
 180                                         return EXIT_FAILURE;
 181                         }
 182                 }
 183
 184                 /* Don't add any further magic if we are in a container */
 185                 return EXIT_SUCCESS;
 186         }
 187
 188         if (read_one_line_file("/sys/class/tty/console/active", &active) >= 0) {
 189                 const char *word, *state;
 190                 size_t l;
 191
 192                 /* Automatically add in a serial getty on all active
 193                  * kernel consoles */
 194                 FOREACH_WORD(word, l, active, state) {
 195                         _cleanup_free_ char *tty = NULL;
 196
 197                         tty = strndup(word, l);
 198                         if (!tty) {
 199                                 log_oom();
 200                                 return EXIT_FAILURE;
 201                         }
 202
 203                         if (isempty(tty) || tty_is_vc(tty))
 204                                 continue;
 205
 206                         if (verify_tty(tty) < 0)
 207                                 continue;
 208
 209                         /* We assume that gettys on virtual terminals are
 210                          * started via manual configuration and do this magic
 211                          * only for non-VC terminals. */
 212
 213                         if (add_serial_getty(tty) < 0)
 214                                 return EXIT_FAILURE;
 215                 }
 216         }
 217
 218         /* Automatically add in a serial getty on the first
 219          * virtualizer console */
 220         NULSTR_FOREACH(j, virtualization_consoles) {
 221                 char *p;
 222
 223                 p = strjoina("/sys/class/tty/", j);
 224                 if (access(p, F_OK) < 0)
 225                         continue;
 226
 227                 if (add_serial_getty(j) < 0)
 228                         return EXIT_FAILURE;
 229         }
 230
 231         return EXIT_SUCCESS;
 232 }